Boom extension control system

ABSTRACT

A boom extension control system for employment with hydraulically extensible booms having hydraulic load lifting cable winches effective to provide an interlock between the boom and winch controls whereby extension of the boom is prevented until the winch is operated.

United States Patent [1 1 Nephew June 11, 1974 [54] BOOM EXTENSION CONTROL SYSTEM 3,601,259. 8/1971 Olson. 212/55 [75] Inventor: Oliver T. Nephew, Cedar Rapids,

Iowa Primary Examiner-Richard E. Aegerter [73] Assignee: FMC Corporation, San Jose, Calif. Assistant Examiner-l-l. S. Lane [22] Filed: Aug 31 1972 Attorney, Agent, or Firm-C. E. Tripp [21] App]. N0.: 285,290

Related US. Application Data I [62] Division of Ser. Nov 10,961, Feb. i2, [970, Pat. No. [57] ABSTRACT A boom extension control system for employment [52] US. Cl. 212/55, 212/31 with hydraulically extensible booms having hydraulic [5 l Int. Cl. A47f 7/00 load lifting cable winches effective to provide an inter- Y [58] Field of Search 212/55, 35, 31 lock between the boom and winch controls whereby extension of the boom is prevented until the winch is 56] References Cited operated.

UNITED STATES PATENTS 3,572.517 3/1971 Liebherr 212/55 X 7 Claims, 5 Drawing Figures 52a .52 AZQI 42a h *itj 1 L I 66 0- 22o.

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RETRACT i izxrsuo a so --l'360. 12411 I ioovm i BOOM EXTENSION CONTROL SYSTEM This is a division of application Ser. No. 10,961 filed Feb. 12, 1970 now US. Pat. No. 3,721,350 issued 3-20-73.

CROSS REFERENCE TO RELATED APPLICATIONS The boom extension control system of the present invention is intended for use with a mobile crane of the type disclosed in Chalupsky et al. application Ser. No. 780.993, which application was filed Dec. 4, 1968 and is assigned to the assignee of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to cranes and more particularly to a control system for operation of an extensible boom and a winch in a crane.

2. Description of the Prior Art Much effort and crane design has been directed to a problem known as two-blocking or doubleblocking." This condition occurs when the lifting block on the end of the winch cable or line is brought into contact with the end of the boom by either extension of the boom, reeling in of the cable, or a combination of both. Two-blocking frequently results in damage to the winch, winch motor and cable. Presently available systems which solve this problem, partially or entirely, are generally complex combinations of hydromechanical and electrical controls that restrict the flexibility of the system, increase the cost of purchase as well as the maintenance cost of the system, and exhibit low reliability due to their complexity and the environment in which cranes are generally operated.

One of the simpler boom control systems is described by Stauffer in US. Pat. No. 3,315,820. The winch is provided with a one-way clutch to prevent unreeling of the cable which may be released either by the winch motor hydraulic circuit when powered in the down direction or by the boom extension circuit whenever the boom is extended. A by-pass relief valve 70 is mounted across the winch motor 27 which permits the cable to be stripped off the winch and the motor to be driven backwardly as a pump when two-blocking occurs due to extension of the boom cylinder. The relief pressure of valve 70 must necessarily be set quite high near the limit of the tensile strength of the winch cable to prevent creeping or dropping of the load whenever the boom cylinder is independently actuated since the winch brake is simultaneously released with extension of the boom cylinder.

SUMMARY OF THE INVENTION It has been determined that the operators of cranes are alert as to the position of the lifting block when operating the winch. Thus, the danger of two-blocking at this time in minimal. However, the operators tend to forget that extension of the boom also causes the lifting block to move upwardly in a direction which might cause two-blocking and, accordingly, the operator sometimes rapidly extends the boom resulting in violent two-blocking" and damage to equipment.

In accordance with a first embodiment of the boom extension control system of the present invention a hydraulic interlock is inserted in the hydraulic system for controlling a boom extension cylinder, a winch brake release cylinder, and a reversible hydraulic winch motor. Separate operator controlled hydraulic valves are provided for extending or retracting the boom, and for releasing the winch brake and activating the winch motor. By opening the valves different amounts, the operator may drive the boom and winch at different speeds. The hydraulic interlock interconnects a boom actuating circuit and a winch actuating circuit and allows extension of the boom only after the operator has consciously manipulated the controls to release the winch brake and activate the winch motor. Thus, in accordance with the first embodiment of the invention the boom cannot inadvertently be extended until the operator actuates the winch motor causing the lifting block to move either up or down at which time the operator is alert as to the position of the lifting block.

The second embodiment of the invention includes an extension control system for controlling the extension of a boom having two separate, independently operated winch and block systems mounted on the same boom. The hydraulic interlock is connected in this system in such a way as to preclude extension of the boom unless the hydraulic winch motors of both winch and block systems are operating in either direction.

The third embodiment of the invention is the same as the first embodiment except that the interlock is arranged to permit boom extension only when the operator controls the winch motor so that the winch is driven in a direction which will lower the lifting block.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic perspective of a mobile crane having an extensible boom and a single block and winch assembly mounted thereon.

FIG. 2 is a schematic view of an extensible boom, winch, and hydraulic control system of the present invention.

I FIG. 3 is a diagrammatic perspective showing the directional relationship of the control handles for the boom and winch.

FIG. 4 is a schematic view similar to FIG. 1 showing a second embodiment of the invention when two winches are employed.

FIG. 5 is a schematic view of an extensible boom, winch and hydraulic control system similar to FIG. 2 modified to illustrate a third embodiment of the invention.

DESCRIPTION OF PREFERRED EMBODIMENT The boom extension control system 10 (FIG. 2) of the present invention is employed in a mobile crane 12 of the type disclosed in FIG. 1. The crane includes a frame 14 mounted on wheels 16 for transportation from place to place. The crane also includes an engine 18 and the usual transmission and drive controls which are generally designated by the numeral 20. Prior to placing the crane in operation for lifting objects, outriggers 21 located at the four corners of the frame 14 are lowered to provide a wider and more stable support for the crane.

A telscoping boom 22 having at least a terminal portion 24 and a base portion 26 is pivotally supported by a turntable 34 for horizontal pivotal movement about an axis 36 and for vertical pivotal movement about an axis 37. Vertical pivotal movement is controlled by two hydraulic cylinders 40 (only one cylinder being shown), and horizontal pivotal movement is controlled by a hydraulic cylinder (not shown). A head block 42 (FIGS. 1 and 2) is mounted on the free end of the terminal portion 24 of the boom 22 and has the free end of a cable or line 44 fixed thereto and trained around one or more pulleys in the head block and around associated pulleys in a lifting block 46 in the usual manner and as diagrammatically illustrated in FIG. 2. The load 48 (FIG. 1) is supported by a hook 50 on the lower end of the lifting block 46.

The cable 44 is wound around a winch 52 journaled on the turntable 34. The winch 52 is driven by a reversible hydraulic motor 54 through a drive shaft 56 and gear box 58 as diagrammatically illustrated in FIG. 2. A brake 60 of standard well known design includes a spring 62 which normally locks the winch 52 from movement in either direction, and a hydraulic winch brake cylinder 64 is provided to release the brake when activated.

A boom extension cylinder 66 is operatively connected to the base portion 26 at 68 and to the terminal portion 24 at 70 and upon activation will telescopically extend or retract the boom 22.

In accordance with the present invention the boom extension control system (FIG. 2) is provided for the purpose of controlling the operation of the boom 22 and winch 52 so that inadvertent extension of the boom is prevented until the operator consciously operates the winch.

The boom extension control system 10 (FIG. 2) of the first embodiment of the invention may broadly be considered to include a boom actuating circuit 80 and a winch actuating circuit 82 interconnected by an interlock circuit 84.

The system 10 includes a driven hydraulic pump 86 which draws hydraulic fluid from a sump S and directs the fluid into the control system through a high pressure conduit 88. If the pressure within the circuit exceeds about 2,000 psi, a pressure relief valve 90 opens to permit the fluid to return directly into the sump S. The high pressure conduit 88 is connected to a manually operated, spring centered, four-way winch valve 92 having a control handle 93 which when in the illustrated neutral position allows high pressure fluid to flow through a conduit 94 into a second manually operated, spring centered four-way boom valve 96 having a control handle 97. When both valves are centered, the high pressure fluid returns to the sump S through conduits 94 and 98. Both four-way valves 92 and 96 may be adjusted by the operator to a parallel passage position or a crosspassage position during which time the fluid flows therethrough in the direction indicated by the arrows. It will also be understood that the fourway valves may be partially or fully opened by the operator by pivoting the valve handles 93 and 97 lesser or greater amounts thereby controlling the rate of flow of fluid therepast.

If it is desired to move the winch 52in a direction which will lower the lifting block 46, the valve 92 of the winch actuating circuit 82 is moved to the parallel passage position. Fluid then flows through a conduit 100, through a check valve 102, into a conduit 104 where it is blocked by check valve 106 but flows through conduit 108 to the single acting winch brake cylinder 64 thereby exerting sufficient pressure to release the brake 60. A hydraulic pressure of about 100 psi in the cylin-, der 64 is sufficient to overcome the pressure of the spring 62. A drain orifice 110 is connected between the conduit 108 and sump S and is provided for the purpose of allowing fluid to be discharged from the brake cylinder 64 thereby relieving pressure in conduit 108 which permits the brake to lock shortly after the valve 92 is moved to its illustrated neutral position. It will, of course, be understood that a small amount of fluid will flow through the drain orifice when the hydraulic motor 54 is operating but this flow is insignificant. The drain orifice 110 is adjusted to maintain the pressure at the brake cylinder 64 above about 100 psi when fluid is flowing through either the parallel or crosspassage positions of the winch valve 92.

When the valve 92 is in its parallel passage position, high pressure fluid also flows through conduit 100 into the hydraulic motor 54 thereby driving the motor in a direction which will transmit power through the shaft 56 and gear box 58, and will drive the winch 52 in a direction which will unwind the cable and lower the lifting block 46.

In order to prevent the load on the lifting block 46 from causing the motor 54 to allow the winch to unwind at high speed, the fluid discharged from the motor 54 flows through conduits 112 and 114 and is prevented from flowing directly into the sump S by a check valve 116. Instead, the fluid discharged from the hydraulic motor 54 flows through a normally closed pilot operated holding valve 1 18. The valve 118 is opened by pressure transmitted through a pilot line 120 when the pressure at the input end of the hydraulic motor 54 is at least about 200 psi. The fluid discharged from the motor then flows through the holding valve 118, through conduits 122, 124, 94 and 98 to the sump S.

When it is desired to raise the lifting block 46, the winch control valve 92 is moved to the cross-passage position. High pressure fluid then flows from conduit 88, through conduit 124, check valve 106, conduit 108 and into the winch brake cylinder 64 to release the winch brake 60. During this time a small amount of fluid flows through the drain orifice 1 10 and is returned to the sump S. High pressure fluid also flows from conduit 124, throughcheck valve 116, conduits 114 and 112, and the hydraulic motor 54 which drives the shaft 56 and the gears in the gear box 58 in a direction which will rotate the winch in a direction raise the lifting block 46. Hydraulic fluid from the motor 54 returns to the sump S through conduit 100, a cross-passage in winch valve 92, and conduits 94 and 98.

When it is desired to operate the boom 22, the boom actuating circuit 80 is energized. In this regard, if it is desired to retract the boom 22, the operator manipu lates the lever 97 (FIGS. 2 and 3) to shift the boom valve 96 into the cross-passage position. High pressure fluid then flows from the pump 86 through conduits 88 and 94, through a cross-passage in the valve 96 and through a conduit into the piston rod end of the cylinder 66 thereby causing the boom cylinder 66 to retract the boom 22. Fluid on the other side of the piston is returned to the sump S through a conduit 132, a pilot actuated check valve 134, a conduit 136, a crosspassage in the valve 96, and the conduit 98.

When it is desired to extend the boom 22, the lever 97 is actuated to place the boom valve 96 in its parallel passage position thereby causing high pressure fluid to flow through conduit 136, through the pilot actuated check valve 134, if the check valve is activated in a manner to be described hereinafter, into the closed end of the boom cylinder 66 to thereby extend the boom 22. The fluid in the other end of the cylinder 66 returns to the sump S through conduits 130 and 98.

An important feature of the first embodiment of the invention is the incorporation of the interlock circuit 84 between the boom actuating circuit 80 and the winch actuating circuit 82, which interlock circuit 84 prevents extension of the boom 22 unless the hydraulic motor 54 is activated and the brake 60 is released The interlock circuit 84 comprises the pilot actuated check valve 134 and a pilot line 138 connecting the check valve 134 to the conduit 108 of the winch actuating circuit 82. The pilot operated check valve is of standard well known design and may be of the type manufactured by Racine Hydraulics & Machinery Inc., of Sarasota, Florida and identified as their 1600 Series Single Pilot Check Valve, which valve requires a 12 to 1 ratio between line pressure and pilot pressure for opening. This pilot operated check valve 134 will allow fluid to flow freely from conduit 132 to conduit 136 at all times thus allowing the boom to be retracted at any time independently of the operation of the winch 52. However, the check valve 134 will preclude flow from the conduit 136 to conduit 132 unless a pilot pressure in pilot line 84 is at least 1/ 12th of the operating pressure in line 136. Thus, the pilot pressure must be at least 166 psi if the system is operating at its maximum pressure of 2,000 psi. As mentioned above, the pressure required to open the brake 60 is about 100 psi. Accordingly, the brake 60 must be released and the hydraulic motor must be driven, in either direction, to maintain a pressure of at least 100 psi in the conduit 108. When the pilot pressure is at its minimum 100 psi brake releasing pressure, which might occur if the valve 92 is adjusted so that very little fluid flows therepast, it will be recognized that the pilot operated check valve 134 will open and the boom may be extended when the pressure in the line 136 is about 1,200 psi. It will be understood, of course, that the pressure within the conduit 108 is usually much greater than 100 psi when the valve 92 is opened.

In operation of the first embodiment of the boom extension control system (FIG. 2) of the present invention it will be assumed that a load is supported by the boom 22 and the lifting block 46, that the winch 52 has previously been operated to lift the load free of the ground, and that the winch valve 92 has been returned to its neutral position. The orifice 110 will then allow the pressure within the winch actuating circuit 82 to drop well below 100 psi causing the spring 62 to move the brake 60 into locking engagement with the shaft 56. The hydraulic motor 54 will, therefore, be stationary at this time.

If the operator then desires to extend the boom 22, movement of the boom valve 96 into the parallel passage position will merely direct high pressure hydraulic fluid from the pump 86 through conduits 88 and 94, a parallel passage in the valve 96, through conduit 136, and into the pilot operated check valve 134 which stops further flow of the fluid since the pressure in the pilot line 138 is not great enough to open the check valve 134. Thus, the boom cannot be extended by merely moving the valve 96 to its parallel passage position. The pressure in conduit 136 will immediately raise to the system pressure of 2,000 psi thereby opening pressure relief valve 90.

In order to extend the boom the operator must not only actuate the boom valve 96 but also must actuate the winch valve 92 by either placing the winch valve in its parallel passage position or in its cross-passage position thereby either lowering or raising the lifting block. If the operator places the winch valve 92 in the parallel passage position, the pressure within the high pressure portion of the winch actuating circuit 82 will almost immediately raise to above at least 200 psi by virtue of the holding valve 118. This pressure is transmitted from the conduit 108 through the pilot line 138 to the pilot operated check valve 134 and is sufficient to open the check valve thereby extending the boom 22 at a rate determined by the amount the lever 97 is moved to the left (FIGS. 2 and 3) by the operator. Similarly, the operator may regulate the rate at which the cable is reeled out by moving the lever 93 of winch valve 92 to the left (FIGS. 2 and 3) the desired amount.

If the operator wishes to raise the load while extending the boom 22, he maintains the valve 96 in the parallel passage position and also moves the winch valve 92 to the cross-passage position. The pressure would then almost immediately raise 200 psi in conduit 108 and conduit 112 thus releasing the brake and causing the winch 52 to move in a direction which will raise the lifting block 46. Since the boom valve 96 is held in the parallel passage position by the operator at this time, the fluid is momentarily blocked by the pilot operated check valve 134 from returning to the sump S, except for a small amount of fluid which flows into the sump S through the orifice 110. However, the pressure rapidly builds up in the conduit 108 and pilot line 138 to above 166 psi thereby providing sufficient pilot pressure to open the pilot valve 134 thus permitting extension of the boom 122.

As mentioned previously, when the operator is manually actuating the winch valve 92 his attention is focused upon the position of the lifting block 46 thus substantially eliminating danger of two-blocking which might occur through inattention if the boom could be 1 extended without at the same time operating the winch It is of course understood that the winch 52 may be operated independently of the boom 22, and that the boom may be retracted at any time independently of the operation of the winch 52.

The boom extension control system 10a (FIG. 4) of the second embodiment of the invention is quite similar to the system 10 of the first embodiment of the invention except that the second embodiment is provided for controlling boom extension when two separate and independent winch and block systems are mounted on a single boom, i.e., when a main winch and block assembly and an auxiliary winch and block assembly 152 are mounted on the same boom 220. Since the single boom system 10 (FIG. 2) of the first embodiment of the invention is incorporated in the control system 10a of the second embodiment of the invention, only the differences between the two systems will be described in detail. The components of the system 10a of the second embodiment of the invention which are equivalent to those of the first embodiment will be assigned the same numerals followed by the letter 0. Furthermore, since the components of the auxiliary winch and block assembly 152 and of the auxiliary winch control circuit 82a are quite similar to those associated with the main winch and block assembly 150, equivalent parts of the auxiliary assembly and winch control circuit will be assigned the same numerals used in the first embodiment of the invention followed by the letter 0.

Although the auxiliary winch and block assembly 152 is diagrammatically illustrated in FIG. 4 as being disposed outwardly of the main winch and the block assembly 150, it will be understood that the two systems are normally placed side by side on the boom 22a with the axes of the pulleys of the head blocks 42a and 42a being concentric. The side by side placement of the main and auxiliary winch and block assemblies 150 and 152 enable an operator to more effectivelyhandle objects such as long pipe line sections since the operator may independently control the two assemblies thereby controllably raising or lowering one end of a pipe section relative to the other end.

Because of the addition of the auxiliary winch and block assembly 152 and the auxiliary winch control circuit 82a, the hydraulic pump 86a and pressure relief valve 90a are connected to an auxiliary winch valve 92a that is operated by a lever 93a (FIGS. 3 and 4) and is connected in series with the winch valve 92a of the main winch and block assembly 150 and with the boom valve 96a of the boom circuit 80a.

An interlock circuit 84a (FIG. 4) is provided and comprises a pilot line 154 which connects conduit 108a of the auxiliary winch control circuit 82a to a manually operated two-way selector valve 156 which includes an auxiliary open position and an auxiliary closed position. When the selector valve 156 is in the illustrated auxiliary open position, a passage 158 in the valve 156 establishes communication between the pilot line 154 and another pilot line 160. When the valve 156 is in the auxiliary closed position, the pilot line 154 is blocked and a U-shaped passage 162 in the valve 156 connects the pilot line 160 with another pilot line 164. The line 164 is connected to the conduit 108a of the main winch control circuit 82a and to a pilot operated check valve 166 which blocks flow of fluid therepast until opened by a pilot pressure which is at least onetwelfth the pressure in the pilot line 164. When the pilot operated check valve 166 is opened, fluid flows through pilot line 168 into the pilot operated check valve 134a of the boom actuating circuit 80a. If the pressure in the pilot line 168 is in excess of one-twelfth of that in the conduit 136a, the check valve 1340 will open and the boom 22a may be extended at a rate determined by the operator as he shifts the valve 96a to its parallel passage position.

In operation of the boom extension control system a, it will first be assumed that the hydraulic pump 86a is operating, that the valve 156 is in its auxiliary open position as illustrated in FIG. 4, and that the valves 96a, 92a, and 92a are in their illustrated neutral positions.

If the operator inattentively attempts to extend the boom 22a by shifting the valve 96a to its parallel passage position without first actuating both of the winch valves 92a and 92a, it will be noted that high pressure fluid will be directed from the pump 86a, through conduits 88a, 94a, 94a, a parallel passage in valve 96a, and into conduit 136a. The pilot operated check valve 134a will block further flow of fluid and accordingly, will prevent the inattentive extension of the boom which might otherwise result in two-blocking.

When the valve 960 is in its parallel passage position, movement of both winch valves 92a and 92a into either their parallel passage or cross passage positions will extend the boom 22a. However, if the operator operates only one of the winch valves and leaves the other winch valve in its neutral position, the boom extension control system 10a prevents the boom 22a from being extended as will be described below. It will be understood that the boom may be extended when one winch valve may be set in a lifting position while the other valve may be set in a lowering position.

For example, if the operator moves the auxiliary valve 92a to its parallel passage position, high pressure fluid will move through the conduit a, check valve 102a, conduit 104a, conduit 108a and will activate brake cylinder 64a to release the brake 600'. A small amount of fluid will bleed through bleed orifice 110a and will return to the sump Sa. However, even though high pressure fluid from conduit 108a is transmitted through pilot line 154, valve passage 158, and line 160 to activate the pilot check valve 166 thereby permitting flow of fluid into the check valve 134a, it will be appreciated that with valve 92a in its neutral position there will be substantially no pressure within the winch control circuit 82a and accordingly pilot operated boom check valve 1340 will not be piloted open. Thus, with one of the winch valves 92a or 92a in its neutral position and with the boom valve 96a in its parallel passage or extended position, the hydraulic motor controlled by the other winch valve will be hydraulically locked.

If at this time, the winch valve 92a is also shifted to either its parallel or cross passage position, sufficient flow and pressure will enter the main winch control circuit to open check valve 134a. If, for example, the valve 92a has been placed in its cross passage position in order to raise the lifting block 46a, high pressure fluid will continue to flow in the auxiliary winch circuit 82a. The high pressure fluid will flow from conduit 100a through the hydraulic motor 54a, through conduits 112a and 114a, through holding valve 118a, through conduits 122a and 124a, through a parallel passage in valve 92a, through conduit 94a and into and through a cross-passage in main winch valve 92a.

Fluid flow will continue through conduit 124a, check valve 106a, conduit 104a and conduit 108a thereby actuating brake cylinder 64a which releases the brake 60a and allowing a small quantity of fluid flows through bleed orifice 110a into sump Sa. A small portion of fluid also flows at high pressure from conduit 108a through pilot line 164, through energizing check valve 166, and through line 168 thereby energizing check valve 134a permitting fluid to flow therepast in an upward direction (FIG. 4) in the boom circuit 80a. High pressure fluid also flows from conduit 1240, through check valve 116a, conduits 114a and 112a, and through hydraulic motor 54a which transmits power through shaft 56a and gearbox 58a to drive the winch 52a in a direction which will raise the lifting block 460. Fluid flows out of the motor 54a through conduit 100a, a cross passage in winch control valve 92a, conduit 94a, a parallel passage in boom valve 96a conduit 136a, ope ii check valve 134a, conduit 132a, and enters the closed end of the boom cylinder 66a thereby extending the boom 22a. Fluid flows from the other end of the boom cylinder 66a through conduit a, a parallel passage in the boom valve 960, and returns to the sump Sa through conduit 98a.

It is apparent, therefore, that in order to energize the pilot operated check valve 134a and thus permit extension of the boom 22a, both the main winch valve 92a and the auxiliary winch valve 92a must be placed in positions other than the illustrated neutral position. As mentioned previously, when the operator is operating the winch valve 920 and 92a his attention is directed to the position of each of the moving lifting blocks 46a and 46a and, accordingly, there will be little danger of two-blocking" at this time. Moreover, since the boom 220 can be extended only at this time, there is little danger of two-blocking due to boom extension.

If a crane that is provided with a boom extension control system 10a (FIG. 4) is to be operated with only its main winch and block assembly 150, the auxiliary winch and block assembly 152 is removed from operative position on the crane and is stored or otherwise deactivated. The two-way selector valve 156 is then shifted to its auxiliary closed position with the U- shaped passage 162 communicating with the pilot lines 160 and 164. Thus, the auxiliary winch circuit 82a is disconnected from the interlock circuit 84a and has no effect upon the operation of the main winch and block assembly 150. When the two-way valve 156 is in its auxiliary closed position, the main winch and block system 150 is controlled in exactly the same manner as occurred with the boom control system of the first embodiment of the invention except that high pressure fluid in conduit 108a must open both pilot check valves 166 and 134a before the boom 22a can be extended.

The boom extension control system 10b (FIG. 5) of the third embodiment of the invention is arranged to permit boom extension only when the winch 52b is driven in a direction which tends to lower the lifting block 46b.

The boom extension control system b (FIG. 5) of the third embodiment of the invention is identical to the first embodiment of the invention except for a change in the interlock circuit 84b, and a change in the location of the pump 86b and pressure relief valve 90b. Accordingly only the differences will be described in detail and parts which are similar to parts of the first embodiment will be given the same numerals followed by the letter b. It will also be noted that the direction of flow of fluid through the valves 92b and 96b is reversed from that of the first embodiment of the invention.

As indicated in FIG. 5 one of the changes between the control system 10 (FIG. 2) and the control system 10b (FIG. 5) is that the motor 86b and pressure relief valve 90b are connected to the conduit 98b, and that the conduit 88b drains directly into the sump Sb. Another change in the two" systems is that the pilot line 138b is connected to the pilot line 12% rather than to the conduit l08b as in the first embodiment of the invention.

In operation, if the operator shifts the boom valve 96b to the cross passage position to extend the boom without first actuating the winch valve 92b, it will be noted that the pilot operated check valve 134 will not be piloted open and accordingly will prevent extension of the boom 22b. The operator 'must then return the boom valve 96b to its illustrated neutral position.

Fluid will then flow through conduits 98b and 94b to the sump Sb through line 88b. If the operator places the winch valve 92b into its parallel passage position thus raising the lifting block 46b, fluid will flow through conduits 124b, check valve 106b, conduit 104b, conduit 108b and will activate brake cylinder 64b to release the brake 60b. Fluid will also flow through conduit 124b, check valve 116b, conduits 1l4b and 11% thereby driving the motor 54b which raises the lifting block 46b. The fluid on the downstream side of the motor 54b will return directly to the sump Sb through conduit b. The pressure in conduit 10% and pilot lines 12% and 138D will accordingly be insufficient to open the pilot operated check valve l34b. Thus, the operator will not be able to extend the boom 22b when the lifting block is moving upwardly since the closed check valve 134b will block the flow of fluid to the boom cylinder 66b.

When the operator places the winch valve 92b in the cross passage position to lower the lifting block 46b, high pressure fluid will flow through conduit 100b, through check valve 102b, conduit l04b and through conduit 108b thereby actuating brake cylinder 64b to release the brake 60b. Fluid will also flow through conduit l00b through motor 54b thereby driving the winch 52b in a direction which will lower the lifting block 46b. The fluid then flows through conduits ll2b and 114b, is blocked by check valve 116b, and accordingly builds up to a pressure of 200 psi which opens holding valve l18b. Fluid then flows through holding valve 118b, conduits 122b and 124b, a cross passage in valve 92b, and returns to the sump Sb. It will be noted that the holding valve ll8b assures that the pressure in conduit 100b and in pilot lines 12% and l38b will be in excess of about 200 psi and will therefore open the pilot operated check valve l34b. Shifting of the boom valve 96b to its cross passage position will permit fluid to flow in the boom circuit 80b through conduit 136b, check valve 134b, conduit 132b and into the boom cylinder 66b thus extending the boom 22b. Fluid is discharged from the boom cylinder 66b through conduit b, a cross passage in the boom valve 96b, through conduit 94b and will return to the sump Sb through the winch circuit 82b and conduit 88b.

Thus, the extension control circuit 10b of the third embodiment of the invention will allow extension of the boom 22b only if the winch is activated to unreel the cable 44, i.e., move the cable in a direction which will tend to lower the lifting block 46b.

Although the direction of fluid in the winch circuits of the several embodiments of the invention have been described in relation to upward or downward movement of the lifting blocks, it will of course be understood that such terms refer to movement of the winch in directions which will respectively, reel in or unwind cable and have been used for more easily visualizing the operation of the control system of the present invention. In this regard, it is to be understood that the lifting block may be maintained at the same elevation when the winch is unwinding cable and the boom is being extended; or conversely, when the cable is being reeled in and the boom is being retracted.

Also, the movement of the pulleys will be affected by pivoting the entire boom about the pivot point 37 (FIG. 1) upon actuation of the cylinders 40 by another circuit (not shown).

From the foregoing description it is apparent that the boom extension control system of the present invention precludes extension of the boom until the operators attention is directed to the position of the lifting block or blocks relative to the boom as occurs when the operator actuates manually operated controls which place the winch or winches on the boom in operation thereby raising or lowering the lifting block or blocks. In this way danger of two-blocking is greatly minimized.

In accordance with the third embodiment of the invention the operator cannot extend the boom unless the winch is driven in a direction which will tend to lower the lifting block.

Although the best mode contemplated for carrying out the present invention has been herein shown and described, it will be apparent that modification and variation may be made without departing from what is regarded to be the subject matter of the invention.

What is claimed is:

l. A boom extension control system for a crane which includes an extensible boom; boom power means for moving said boom between an extended and a retracted position; a winch and block assembly on said crane with the block assembly including a lifting block suspended from said cable on the free end of said boom; a brake for normally holding said winch and block assembly from movement relative to said boom; brake power means for releasing said brake; winch power means for selectively rotating said winch in a direction which will raise or lower said lifting block; the improvement which comprises control means including a boom actuating circuit activated by a manually operated boom control, a winch and brake actuating circuit activated by a manually operated winch control, an interlock circuit connecting said boom circuit to said winch circuit, said interlock circuit being effective to preclude extension of said boom until said boom control and said manually operated winch control are manipulated to operate said brake power means and said winch power means, an auxiliary winch and block assembly on said crane with the auxiliary block assembly including an auxiliary lifting block suspended from an auxiliary cable on the free end of said boom, an auxiliary brake for normally holding said auxiliary winch and block assembly from movement relative to said boom; auxiliary brake power means for releasing said auxiliary brake; auxiliary winch power means for selectively rotating said auxiliary winch in a direction which will raise or lower said auxiliary lifting block; and wherein said control means additionally comprises an auxiliary winch and brake actuating circuit which is activated by a manually operated auxiliary winch control; and wherein said interlock circuit is also connected to said auxiliary winch and brake circuit and is effective to preclude extension of said boom until said manually operated auxiliary winch control is manipulated to activate said auxiliary brake power means and said auxiliary winch power means simultaneously with the manipulation of said manually operated winch control to operate said brake power means and said winch power means.

2. A boom extension control system according to claim I wherein all of said power means and said control means are hydraulically operated; and wherein said manually operated boom control, said winch control, and said auxiliary winch control are valves for changing the direction of flow of fluid through said control system.

3. A boom extension control system according to claim 2 wherein said boom actuating circuit includes a first pilot operated check valve which normally precludes flow of fluid therethrough in a direction which will extend the boom; and wherein said interlock circuit includes a first pilot line connecting said first check valve to said winch circuit, a second pilot operated check valve in said first pilot line for precluding flow of fluid and application of pressure to said first check valve until piloted open, and a second pilot line con necting said second check valve to said auxiliary winch circuit for opening said second check valve when a pilot pressure within said auxiliary winch circuit is above a predetermined amount allowing fluid from said winch circuit to flow through said second check valve for piloting said first check valve open when the pilot pressure within said winch circuit is above a predetermined pilot pressure thereby precluding extension of said boom until said predetermined pilot pressure is present in both the winch and the auxiliary winch circuits.

4. A boom extension control system according to claim 3 wherein said first pilot line has an open end, and additionally comprising a two-position manually operated selector valve connected to said first and second pilot lines, said selector valve having an auxiliary on position wherein flow through said open end of said first pilot line is blocked and wherein said second pilot line is open to permit flow of fluid therethrough, said selector valve having an auxiliary off position wherein fluid flow from said auxiliary winch circuit is precluded and wherein said second pilot line communicates with the open end of said first pilot line thereby permitting extension of said boom independent of pressure conditions within said auxiliary winch circuit.

5. A boom extension control system for a crane comprising an extensible boom including a terminal portion and a base portion; reversible operating boom pilot means for moving said terminal portion between an extended position and a retracted position; a winch on said crane; a cable wound on said winch; a head block supported by said terminal portion and having a portion of the cable trained therearound with the free end of the cable secured to said boom; a lifting block supported by said cable for vertical movement relative to said boom; a brake for normally holding said winch stationary; a brake power means for releasing said brake; winch power means for rotating said winch in either direction; and control means including manually operated controls connected to said boom power means, said brake power means, and said winch power means; said control means being unaffected by the position of said lifting block and including interlock means which is effective to preclude extension of said boom until said manually operated controls are manipulated to ac-' tivate said brake power means and said winch power means; an auxiliary winch on said crane; an auxiliary cable wound on said auxiliary winch; an auxiliary head block supported by said terminal portion and having a portion of the auxiliary cable trained therearound with the free end of the auxiliary cable secured to said boom; an auxiliary lifting block supported by said auxiliary cable for vertical movement relative to said boom; an auxiliary brake for normally holding said auxiliary winch stationary; an auxiliary brake power means for releasing said auxiliary brakes; auxiliary winch power means for rotating said auxiliary winch in either direction; and wherein said control means includes a manually operated auxiliary control connected to said auxiliary brake power means and auxiliary winch power means; and wherein said interlock means is arranged to preclude extension of said boom until said auxiliary manually operated control is manipulated to activate said auxiliary brake power means and said auxiliary winch power means simultaneously with the actuation of said brake power means and said winch power means.

6. In a crane having an extensible boom and having power means for extending or retracting said boom, said crane having a main reversibly operated winch with a main cable attached to said boom, said main cable supporting a vertically movable main lifting block, said crane having an auxiliary reversibly operated winch with an auxiliary cable attached to said boom, said cable supporting a vertically movable auxiliary lifting block, a boom hydraulic circuit including a shiftable hydraulic boom valve for the introduction of pressure fluid for selective operation of said boom, a main winch hydraulic circuit including a shiftable main hydraulic winch valve for the introduction of pressure fluid for selective operation of said main winch, and an auxiliary winch circuit including a shiftable hydraulic auxiliary winch valve for the introduction of pressure fluid for selective operation of said auxiliary winch, a pilot operated valve in said boom circuit normally positioned to block the transmission of fluid in said boom circuit, and means operable in response to fluid pressure in both of said winch circuits to shift said pilot operated valve to permit the transmission of fluid pressure in the boom circuit for the extension of said boom.

7. In a crane having an extensible boom and having power means for extending or retracting said boom, said crane having a main reversibly operated winch with a main cable attached to said boom, said main cable supporting a vertically movable main lifting block, said crane having an auxiliary reversibly operated winch with an auxiliary cable attached to said boom, said cable supporting a vertically movable auxiliary lifting block, a boom hydraulic circuit including a shiftable hydraulic boom valve for the introduction of pressure fluid for selective operation of said boom, 21 main winch hydraulic circuit including a shiftable main hydraulic winch valve for the introduction of pressure fluid for selective operation of said main winch, and an auxiliary winch circuit including a shiftable hydraulic auxiliary winch valve for the introduction of pressure fluid for selective operation of said auxiliary winch, the improvement comprising a pilot line between said auxiliary winch circuit and said main winch circuit and a pilot line between said main winch circuit and said boom circuit, a pilot operated valve in said boom circuit normally positioned to block the transmission of fluid in said circuit, said pilot operated valve shiftable in response to pressure in one of said pilot lines to permit the transmission of fluid in the circuit for extension of said boom, and a valve in said one pilot line to transmit fluid pressure to said pilot operated valve in the boom circuit in response to pressure in the other pilot line. 

1. A boom extension control system for a crane which includes an extensible boom; boom power means for moving said boom between an extended and a retracted position; a winch and block assembly on said crane with the block assembly including a lifting block suspended from said cable on the free end of said boom; a brake for normally holding said winch and block assembly from movement relative to said boom; brake power means for releasing said brake; winch power means for selectively rotating said winch in a direction which will raise or lower said lifting block; the improvement which comprises control means including a boom actuating circuit activated by a manually operated boom control, a winch and brake actuating circuit activated by a manually operated winch control, an interlock circuit connecting said boom circuit to said winch circuit, said interlock circuit being effective to preclude extension of said boom until said boom control and said manually operated winch control are manipulated to operate said brake power means and said winch power means, an auxiliary winch and block assembly on said crane with the auxiliary block assembly including an auxiliary lifting block suspended from an auxiliary cable on the free end of said boom, an auxiliary brake for normally holding said auxiliary winch and block assembly from movement relative to said boom; auxiliary brake power means for releasing said auxiliary brake; auxiliary winch power means for selectively rotating said auxiliary winch in a direction which will raise or lower said auxiliary lifting block; and wherein said control means additionally comprises an auxiliary winch and brake actuating circuit which is activated by a manually operated auxiliary winch control; and wherein said interlock circuit is also connected to said auxiliary winch and brake circuit and is effective to preclude extension of said boom until said manually operated auxiliary winch control is manipulated to activate said auxiliary brake power means and said auxiliary winch power means simultaneously with the manipulation of said manually operated winch control to operate said brake power means and said winch power means.
 2. A boom extension control system according to claim 1 wherein all of said power means and said control means are hydraulically operated; and wherein said manually operated boom control, said winch control, and said auxiliary winch control are valves for changing the direction of flow of fluid through said control system.
 3. A boom extension control system according to claim 2 wherein said boom actuating circuit includes a first pilot operated check valve which normally precludes flow of fluid therEthrough in a direction which will extend the boom; and wherein said interlock circuit includes a first pilot line connecting said first check valve to said winch circuit, a second pilot operated check valve in said first pilot line for precluding flow of fluid and application of pressure to said first check valve until piloted open, and a second pilot line connecting said second check valve to said auxiliary winch circuit for opening said second check valve when a pilot pressure within said auxiliary winch circuit is above a predetermined amount allowing fluid from said winch circuit to flow through said second check valve for piloting said first check valve open when the pilot pressure within said winch circuit is above a predetermined pilot pressure thereby precluding extension of said boom until said predetermined pilot pressure is present in both the winch and the auxiliary winch circuits.
 4. A boom extension control system according to claim 3 wherein said first pilot line has an open end, and additionally comprising a two-position manually operated selector valve connected to said first and second pilot lines, said selector valve having an auxiliary on position wherein flow through said open end of said first pilot line is blocked and wherein said second pilot line is open to permit flow of fluid therethrough, said selector valve having an auxiliary off position wherein fluid flow from said auxiliary winch circuit is precluded and wherein said second pilot line communicates with the open end of said first pilot line thereby permitting extension of said boom independent of pressure conditions within said auxiliary winch circuit.
 5. A boom extension control system for a crane comprising an extensible boom including a terminal portion and a base portion; reversible operating boom pilot means for moving said terminal portion between an extended position and a retracted position; a winch on said crane; a cable wound on said winch; a head block supported by said terminal portion and having a portion of the cable trained therearound with the free end of the cable secured to said boom; a lifting block supported by said cable for vertical movement relative to said boom; a brake for normally holding said winch stationary; a brake power means for releasing said brake; winch power means for rotating said winch in either direction; and control means including manually operated controls connected to said boom power means, said brake power means, and said winch power means; said control means being unaffected by the position of said lifting block and including interlock means which is effective to preclude extension of said boom until said manually operated controls are manipulated to activate said brake power means and said winch power means; an auxiliary winch on said crane; an auxiliary cable wound on said auxiliary winch; an auxiliary head block supported by said terminal portion and having a portion of the auxiliary cable trained therearound with the free end of the auxiliary cable secured to said boom; an auxiliary lifting block supported by said auxiliary cable for vertical movement relative to said boom; an auxiliary brake for normally holding said auxiliary winch stationary; an auxiliary brake power means for releasing said auxiliary brakes; auxiliary winch power means for rotating said auxiliary winch in either direction; and wherein said control means includes a manually operated auxiliary control connected to said auxiliary brake power means and auxiliary winch power means; and wherein said interlock means is arranged to preclude extension of said boom until said auxiliary manually operated control is manipulated to activate said auxiliary brake power means and said auxiliary winch power means simultaneously with the actuation of said brake power means and said winch power means.
 6. In a crane having an extensible boom and having power means for extending or retracting said boom, said crane having a main reversibly operated winch with a main cable attacheD to said boom, said main cable supporting a vertically movable main lifting block, said crane having an auxiliary reversibly operated winch with an auxiliary cable attached to said boom, said cable supporting a vertically movable auxiliary lifting block, a boom hydraulic circuit including a shiftable hydraulic boom valve for the introduction of pressure fluid for selective operation of said boom, a main winch hydraulic circuit including a shiftable main hydraulic winch valve for the introduction of pressure fluid for selective operation of said main winch, and an auxiliary winch circuit including a shiftable hydraulic auxiliary winch valve for the introduction of pressure fluid for selective operation of said auxiliary winch, a pilot operated valve in said boom circuit normally positioned to block the transmission of fluid in said boom circuit, and means operable in response to fluid pressure in both of said winch circuits to shift said pilot operated valve to permit the transmission of fluid pressure in the boom circuit for the extension of said boom.
 7. In a crane having an extensible boom and having power means for extending or retracting said boom, said crane having a main reversibly operated winch with a main cable attached to said boom, said main cable supporting a vertically movable main lifting block, said crane having an auxiliary reversibly operated winch with an auxiliary cable attached to said boom, said cable supporting a vertically movable auxiliary lifting block, a boom hydraulic circuit including a shiftable hydraulic boom valve for the introduction of pressure fluid for selective operation of said boom, a main winch hydraulic circuit including a shiftable main hydraulic winch valve for the introduction of pressure fluid for selective operation of said main winch, and an auxiliary winch circuit including a shiftable hydraulic auxiliary winch valve for the introduction of pressure fluid for selective operation of said auxiliary winch, the improvement comprising a pilot line between said auxiliary winch circuit and said main winch circuit and a pilot line between said main winch circuit and said boom circuit, a pilot operated valve in said boom circuit normally positioned to block the transmission of fluid in said circuit, said pilot operated valve shiftable in response to pressure in one of said pilot lines to permit the transmission of fluid in the circuit for extension of said boom, and a valve in said one pilot line to transmit fluid pressure to said pilot operated valve in the boom circuit in response to pressure in the other pilot line. 